In the typical fuel vapor vent valve for a motor vehicle fuel tank that is adapted to prevent spillage in case of shaking, tilting or rollover of the vehicle, the valve normally opens the fuel tank to an orifice that is connected by a vapor exit passage in the valve body to a vapor hose leading to a fuel vapor storage device. The valve body is commonly made as a one-piece plastic injected molded part that has a simple direct connection between the orifice and the vapor exit passage. However, this connection has a tendency to collect and pass any liquid fuel issuing from the orifice under pressure from the tank on to the vapor storage canister. The latter contains a fuel vapor absorber such as carbon and any liquid fuel delivered thereto will quickly reduce its vapor absorbing ability. An example of such vent valve is disclosed in U.S. Pat. No. 5,044,389 granted to David R. Gimby Sep. 3, 1991 for a high volume fuel vapor release valve and assigned to the assignee of the present invention.
It is difficult to configure the top of the molded body with a vapor exit passage connection that would somehow trap this liquid fuel after it passes through the orifice and then drain the trapped liquid fuel back to the tank. This is also the case where the valve is omitted and only venting is provided through an orifice in a vent body that mounts on the fuel tank.
As to any such possible liquid fuel drainage back to the tank in the case of a vent assembly having a valve that blocks the orifice on overfill, vehicle shaking, tilting and/or rollover, adversely affecting the operation of the valve for normal venting operation in an upright position and closure under these various circumstances must be considered. Any drainage path for liquid fuel trapped downstream of the orifice can not provide a path for fuel vapor to vent around the closed valve in the normal upright attitude of the tank or allow liquid fuel to escape from the tank when tipped or inverted.
One solution to such problem is set forth in U.S. Pat. No. 5,413,137 granted to David R. Gimby May 9, 1995 for a fuel vapor vent assembly with liquid trap; also assigned to the assignee of the present invention. The fuel vapor vent assembly set forth in the '137 patent embodies a fuel impervious insert that is adapted to be mounted in such a vent valve body and defines both a vertically oriented vent orifice and a liquid basin extending about the exit of this orifice. A simple cavity formed in the interior of the top of the plastic body cooperates with the basin in the insert to define an expansive chamber elevated above the orifice with a horizontal vapor exit passage in the plastic body adapted to be connected to a vapor storage device. The expansive chamber forms an elevated liquid trap at the exit of the orifice that traps liquid from the venting fuel vapor while permitting venting to continue therethrough and then drains the trapped liquid in the basin back into the tank through the orifice in the insert when the pressure in the fuel tank is relieved. The liquid trapping chamber has a ceiling directly opposite the orifice dead ending the vapor stream issuing therefrom and the vapor exit passage is connected to the expansive chamber at a point above the basin. These features combine to aid in separating any liquid fuel out from the vapor and down into the basin and prevent it from passing on to the vapor exit passage and thence to the vapor storage canister.
While suitable for their intended purpose, the fuel vapor vent assemblies set forth in the aforesaid prior art Gimby patents do not include provision for venting vapor from the tank as the float is closing at the same rate at which the fuel tank is being filled nor do they provide a predetermined vapor dome space within said tank to accommodate vapor pressure increases when the refueling valve is closed. Further, the unitary body arrangements are configured to locate the valve seat close to the tank top and the fuel vapor openings well below the valve seat so that venting is restricted as the float moves between its normally open position and its normally closed position. Moreover, the valve disclosed in the Gimby '389 patent has a direct path for liquid fuel to splash through the fuel vapor openings of the valve body into the vapor outlet past the valve seat.
Furthermore, the valves disclosed in the aforementioned Gimby patents use a unitary housing that does not accommodate side impacts to the fuel tank that tend to displace the housing portion in the fuel tank in the lateral direction.
In our prior patent application, Ser. No. 08/555,129 filed Nov. 8, 1995 for a vehicle refueling valve, now U.S. Pat. No. 5,678,756 issued Nov. 18, 1997, we provided several improvements for the vent valves of the type discussed above. However, each of the improved valves also used either a unitary or a two piece housing that did not accommodate side impacts the fuel tank. The two piece housings comprised a cover member that was permanently fixed to the fuel tank and a cylindrical member that was disposed inside the fuel tank. However, in each instance the cylindrical member was secured firmly to the cover member so that the two piece housing was substantially the same as a unitary housing with regard to side impacts.
In our first continuation in part application, U.S. patent application Ser. No. 08/922,772 filed Sep. 3, 1997 we proposed several improvements and enhancements to the refueling valve that is disclosed in the '756 patent. These improvements and enhancements are repeated in this second continuation-in-part application.
In this second continuation-in-part application we also address side impacts to the fuel tank. Regarding this further aspect, an object of the invention is to provide a fuel vapor vent device that has a two piece housing comprising a cover and a body in which the body includes a float containing section and is connected to the cover in such a manner so as to accommodate side impacts within the fuel tank while maintaining the ability to effect closure of the valve.